The use of surgical fixation plates for a variety of orthopedic applications is widely accepted. The plates are used by surgeons to mend, align, and alter compression of patient's bones, and are typically fastened to the bones with a plurality of fasteners such as screws that are installed through holes in the plate. Proper orientation and alignment of fasteners and secure surgical fixation of the plates is advantageous in avoiding future complications after implantation.
Bone plates used in spinal applications must be installed with special care, as the plates are used for long term, intervertebral fixation, bone-fragment fixation, and anterior decompression in the cervical region of the spine. The margin for error in spinal surgery is quite small, particularly because of the sensitivity of the spinal cord and the risk inherent with invasive procedures around the spinal cord. In particular, the dimensions of vertebral bone available for setting fasteners are fairly limiting.
Each fixation fastener should properly align with its associated plate hole so that each screw is seated correctly with the plate and enters the bone at an appropriate angle. Any misalignment of the screw within the plate hole risks tissue damage. In addition, improperly seated screws may result in an unstable or insecure connection of the plate to the bony material, thus potentially defeating the usefulness of the plate. Locking plates, in particular, demand precise fastener alignment.